I've wondered since a long time how much fuel a fighter aircraft can take to the skies. Looking at the MiG-25 Foxbat, I'm asking how its tanks can store enough fuel for more than 50 miles of combat radius:

Every fighter jet is different. For the MiG-25 most of the fuel is in the fuselage

You can see how the fuel tanks are outlined "hugging" the intake outline in the area after the intake entrance but before the engines. The rest is in the wings, as thin as they are. It looks deceiving but there's still a lot of space in there because they are a large area. The wing tanks hold a total of 4920L of fuel...almost 5 tons! The entire capacity for the MiG-25 is 17,780L and the range is about 1600km when flying supersonic.

Some fighters like the MiG-29 and F-22 are notorious for their short range. Often you will find fighters carrying external drop tanks to increase range. Common practice on all of them.

With most fighters, the majority of the fuselage space between the cockpit and the engine bays is generally dedicated to fuel. The designers endeavour to jam fuel tankage in just about any little nook and cranny that they can, which makes for some maintenance nightmares when there are fuel leaks.

The wings are generally a small(ish) fraction of total internal tankage. A couple of examples I can think of are the F-111 at about 20% of total internal fuel, and the SuperHornet at about 27 to 30%. (Those numbers are straight off the top of my head, dont trust them too far)